<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    {% block container %}
    <div id="container">
        {% block top %}
        <div id="top">
            <p>草</p>
        </div>
        {% endblock %}
        {% block left %}
        <div id="left">
            <p>树</p>
        </div>
        {% endblock %}
        {% block right %}
        <div id="right">
            <p>花</p>
        </div>
        {% endblock %}
    </div>
    {% endblock %}

</body>
</html>